Why are Elasmobranchs important?
Elasmobranchs are a fundamental link in marine ecosystems. Without them the marine ecosystem loses its balance. As apex and meso predators, they help maintain the species below them in the food chain – keeping populations in check and healthy.
They serve as a key indicator for ocean health. Several studies have shown that declining populations of sharks can cause disastrous consequences, including the collapse of fisheries and the death of coral reefs.
Sharks also have major cultural significance and tourism value.
Are Irish Elasmobranchs at risk?
Elasmobranchs, and Chimaeras, have difficult life histories. They grow slowly, mature late in life, reproduce infrequently, have relatively low fertility and can have relatively long life spans. All of these factors result in very low natural population growth rates.
Beyond these significant natural challenges, they face multiple threats caused by humans, including overfishing, pollution and habitat destruction.
39 species of sharks, 33 species of skates and rays, and 8 species of Chimaera (correct as of Feb 23) are found in Irish territorial waters – 80 species of cartilaginous fish in total, which is over half of the European list, and about 7% of the worldwide total,
In the most recent regional report by the IUCN Red List of Threatened Species (the world’s most comprehensive inventory of the global conservation status of biological species) has found 37% of Cartilaginous fish to be threatened. The irish assessment elasmobranchs in Irish waters (NPWS,2016), found that of the 58 species assessed…..:
6 species are Critically Endangered:
- Portuguese dogfish (Centroscymnus coelolepis)
- Common (blue) skate (Dipturus batis (= flossada))
- Flapper skate (Dipturus intermedia)
- Porbeagle shark (Lamna nasus)
- White skate (Rostroraja alba)
- Angel shark (Squatina squatina)
5 species are Endangered:
- Leafscale gulper shark (Centrophorus squamosus)
- Basking shark (Cetorhinus maximus)
- Common stingray (Dasyatis pastinaca)
- Undulate skate (Raja undulata)
- Spurdog (Squalus acanthias)
6 species are Vulnerable:
- Longnose velvet dogfish (Centroselachus crepidater)
- Kitefin shark (Dalatias licha)
- Tope (Galeorhinus galeus)
- Shagreen ray (Leucoraja fullonica)
- Longnose skate (Dipturus oxyrinchus)
- Cuckoo ray (Leucoraja naevus)
Of the remaining species, 19 are assessed as Near Threatened and 22 species as Least Concern.
How are Elasmobranchs at risk?
There are no longer any directed fisheries for any threatened cartilaginous fish in Irish waters. However threatened species are taken as by-catch in several fisheries, involving both Irish and non-Irish vessels. Bycatch is the accidental catch of an animal by fisher when fishing another species. Worldwide, an estimated 50 million sharks are accidentally caught in trawl nets, on longline hooks and in fishing gillnets every year. This accidental capture by fishing gear is the greatest threat to most Elasmobranchs, and this pressure is increasing as fishing activity expands, particularly in Irish waters where a large proportion of European fishing effort is focused. European Angelsharks and large Skate species have become Critically Endangered due mainly to bycatch in unselective bottom trawls. Blue sharks also make up a large percentage of the bycatch in EU pelagic longline fisheries for tuna and swordfish.
Coastal development and other human activities have directly destroyed or disturbed Elasmobranch habitats around the world. Feeding and nursery grounds, such as sea grass beds, are damaged and destroyed by pollution and human activity. Coastal development has increased significantly in the past century, which has altered habitats, increased levels of pollution and resulted in the general environmental degradation in many areas. As slow growing animals, Elasmobranchs are very susceptible pollution and environmental contamination. Pollution in the ocean has either filtered from land activities or has been directly deposited into the seas.
Unfortunately Elasmobranchs continue to be harvested both for human consumption and trade of their parts. Sharks and rays are fished commercially throughout Europe for their meat, livers, cartilage and fins. There is a particularly strong demand in Asia for shark fins, which are used to make shark fin soup, a traditional Chinese delicacy, and so many sharks are shipped to the Asian market.
Spain, France, Portugal, and the UK rank among the top 20 ‘shark’ (includes rays and chimaeras) fishing countries, putting the EU second in the world for landings of these species. Spain ranks third overall with 7.3% of the total global shark catch. Irish vessels land substantial amounts of skates and rays.
In Ireland, ray wings and dogfish meat (often called Rock salmon or Huss) are sold in fish shops, whereas the livers and fins of oceanic sharks are exported to other countries. There is also an important recreational fishery in Ireland and sea angling is very popular during the summer months, but most educated anglers follow the catch and release policy.
In 2013, the European Parliament and Council of Fisheries Ministers agreed to a regulation requiring that all sharks caught in EU waters or by EU boats globally had to be landed with their fins naturally attached, with no exceptions. This regulation was a great achievement for the Elasmobranch conservation community, yet more needs to be done by the EU to prevent decimation of stocks, such as tighter regulation and strict enforcement.
Temperature plays a major role in the life of Elasmobranchs. The warming water temperatures caused by climate change are disrupting their behaviours, habitats and food sources. Increased levels of carbon dioxide in the seas are also causing the water to become more acidified, having further effects on body condition, growth, and behaviour of Elasmobranchs.